Definition

1. Noun:
   • The ratio of the focal length to the diameter of a camera lens system: This numerical value, also called the focal ratio or f-stop, indicates the size of the lens aperture. A lower f-number (e.g., f/2.8) means a larger aperture opening, allowing more light to enter. A higher f-number (e.g., f/16) means a smaller aperture opening, allowing less light to enter. It is a critical setting in photography that controls exposure and depth of field.

Usage Examples

• Noun:
  • To capture more light in this dark room, use a lens with a lower f number, like f/1.8.
  • For a landscape photo with everything in focus, you should set a high f number, such as f/11.
  • The photographer adjusted the f number on her camera to change the depth of field.

Advanced Usage

• "To stop down": To decrease the aperture size, which increases the f-number.

  • He stopped down to f/16 to get a sharper image across the entire scene.

• "Wide open": Using the lens at its maximum aperture (lowest possible f-number).

  • She shot the portrait wide open at f/2 to create a soft, blurred background.

Variants and Related Words

• F-stop (n): A common synonym for f-number, often used interchangeably.

  • What f-stop did you use for that shot?

• Aperture (n): The opening in a lens through which light passes. The f-number is the measure of this opening's size.

  • The aperture is controlled by the f-number setting.

• Focal ratio (n): A technical term synonymous with f-number, often used in optics.

  • The telescope has a focal ratio of f/10.

Synonyms

• F-stop: The most common direct synonym.
• Focal ratio: A more technical synonym.
• Aperture value: A descriptive synonym referring to the numerical setting.

Related Phrases

• Depth of field: The area of acceptable sharpness in a photo, which is directly controlled by the f-number.

  • A low f number produces a shallow depth of field.

• Exposure triangle: The relationship between aperture (f-number), shutter speed, and ISO that determines a photograph's exposure.

  • Understanding the f number is key to mastering the exposure triangle.

Noun

1. the ratio of the focal length to the diameter of a (camera) lens system